In some aspects, a resonator device includes a dielectric substrate, a ground plane on a first side of the substrate, and conductors on a second, opposite side of the substrate. The conductors include first and second resonators and two baluns. Each balun includes a feed, a first branch and a second branch. The feed is connected to the first and second branches, and the first and second branches are capacitively coupled to the respective first and second resonators. The first branch includes a delay line configured to produce a phase shift relative to the second branch. The resonator device includes a sample region configured to support a magnetic resonance sample between the first and second resonators.
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1. A resonator device comprising:
a dielectric substrate;
a ground plane on a first side of the substrate;
conductors on a second, opposite side of the substrate, the conductors comprising:
first and second resonators; and
two baluns, each respective balun comprising a feed, a first branch and a second branch, the feed of each balun connected to the first and second branches of the balun, the first and second branches of each balun capacitively coupled to the respective first and second resonators, the first branch of each balun comprising a delay line configured to produce a phase shift relative to the second branch of the balun; and
a sample region configured to support a magnetic resonance sample between the first and second resonators.
13. A resonator device comprising:
a first resonator;
a second resonator;
a sample region configured to support a magnetic resonance sample between the first and second resonators; and
means for delivering microwave signals to the first and second resonators, wherein the microwave signals delivered to the first resonator comprise a phase shift relative to the microwave signals delivered to the second resonator,
wherein the means for delivering microwave signals comprises:
a first balun comprising a first pair of branches capacitively coupled to the respective first and second resonators; and
a second balun comprising a second pair of branches capacitively coupled to the respective first and second resonators,
wherein the first and second resonators and the first and second baluns comprise superconducting material on a dielectric substrate.
2. The resonator device of
the delay line of each balun extends between first and second ends of the delay line;
the first branch of each respective balun comprises:
a first portion connected between the feed of the balun and the first end of the delay line of the balun;
a second portion connected to the second end of the delay line of the balun, extending to a gap between the first branch of the balun and the first resonator; and
the second branch of each balun extends from the feed of the balun to a gap between the second branch of the balun and the second resonator.
3. The resonator device of
a first delay line portion that extends from the first end of the delay line of the balun, perpendicular to the first portion of the first branch of the balun;
a second delay line portion that extends from the second end of the delay line of the balun, perpendicular to the second portion of the first branch of the balun; and
one or more turns between the first and second delay line portions of the balun.
4. The resonator device of
a third delay line portion that extends from the first delay line portion of the balun, perpendicular to the first delay line portion of the balun;
a fourth delay line portion that extends from the second delay line portion of the balun, perpendicular to the second delay line portion of the balun; and
one or more turns between the third and fourth delay line portions of the balun.
5. The resonator device of
6. The resonator device of
7. The resonator device of
8. The resonator device of
9. The resonator device of
11. The resonator device of
12. The resonator device of
14. The resonator device of
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This application claim priority to U.S. Provisional Application No. 62/196,166, filed on Jul. 23, 2015, which is hereby incorporated by reference.
The following description relates to a resonator device for magnetic resonance applications.
Magnetic resonance systems are used to study various types of samples and phenomena. In some magnetic resonance applications, the spins in a sample are polarized by a static, external magnetic field, and a resonator manipulates the spins by producing a magnetic field at a frequency near the spins' resonance frequencies. Resonators can be used, for example, in electron spin resonance (ESR), nuclear magnetic resonance (NMR), magnetic resonance imaging (MRI) and other applications.
In some aspects of what is described here, a resonator device includes a balun. The resonator device can be, for example, a resonator device for electron spin resonance (ESR) applications, nuclear magnetic resonance (NMR) applications, magnetic resonance imaging (MRI) applications or another application. In some examples, a resonator device includes two resonators that are parallel to each other and fed differentially by baluns configured to operate at the resonant frequency of the resonators. In the examples shown in
In some implementations, a resonator device having a high quality factor can produce a magnetic field that has a low mode volume. The resonator device can be used for magnetic applications to produce a microwave or radio frequency magnetic field that is substantially homogeneous across the sample in all three spatial dimensions. In some cases, the resonator device is less sensitive to DC (static) magnetic fields aligned along the direction of current flow in the conductors of the resonator device. For instance, the arrangement of conductors in the resonator device can reduce vortex losses.
In some implementations, the dielectric substrate 160 includes a cavity or recess in the sample region 105, and the sample 110 can be positioned in the cavity or recess. The sample 110 can be, for example, a three dimensional sample containing a spin ensemble that is distributed over three spatial dimensions. In some examples, the sample 110 has a thickness (in the y-direction) of 100 micrometers (100 μm) and sits in a recess having a depth of 50 micrometer (50 μm) in the substrate 160. Another size sample may be used. The resonator device 100 may be configured to produce a substantially uniform microwave magnetic field over the full three-dimensional spatial extent of the sample 110. In some examples, the resonator device 100 produces a microwave magnetic field that is substantially uniform over a region that is 100 micrometers (100 μm) thick in the y-direction.
In some implementations, the dielectric substrate 160 is made of dielectric material such as, for example, sapphire, silicon, MgO2, LaAlO3, or another type of non-magnetic dielectric crystalline material. In some implementations, the conducting material on the dielectric substrate (e.g., the ground plane 170, the conductors 150, etc.) can be made of non-superconducting material (e.g., gold, copper, etc.), superconducting material (e.g., niobium, niobium titanium, niobium nitride, aluminum, yttrium barium copper oxide (aka, “YBCO”), magnesium diboride) or a combination of them. The conducting materials can be deposited on the substrate 160 by standard deposition processes. The substrate 160 can be etched or otherwise conditioned based on standard fabrication processes.
In some implementations, the ground plane 170 and the conductors 150 can be implemented as thin films on opposite sides of the dielectric substrate 160. In the example shown in
As shown in
In the example shown, the resonators 115A, 115B are implemented as conductor strips supported on the dielectric substrate 160. The example resonators 115A, 115B in
In the example shown, the first and second baluns 102A, 102B are implemented as conductors having similar structures; the first and second baluns 102A, 102B have identical designs and opposite orientations on the dielectric substrate 160. The first and second baluns 102A, 102B reside at opposite ends of the elongate resonators 115A, 115B; the first balun 102A is coupled to the resonators 115A, 115B across the gaps at a first end of the resonators 115A, 115B, and the second balun 102B is coupled to the resonators 115A, 115B across the gaps at a second, opposite end of the resonators 115A, 115B.
The first balun 102A includes a feed 111A, two branches connected to the feed 111A, and a power splitter section between the feed 111A and the two branches. The branches of the first balun 102A are capacitively coupled to the respective first and second resonators 115A, 115B. A first branch extending from the feed 111A includes a first delay line 113A, and a second branch extending from the feed 111A includes a conducting strip 114A. The conducting strip 114A extends from the feed 111A to the gap between the branch and the second resonator 115B. The delay line 113A in the first branch is configured to produce a phase shift relative to the conducting strip 114A in the second branch.
Similar to the first balun 102A, the second balun 102B includes a feed 111B, two branches connected to the feed 111B, and a power splitter section between the feed 111B and the two branches. The branches of the second balun 102B are capacitively coupled to the respective first and second resonators 115A, 115B. A first branch extending from the feed 111B includes a second delay line 113B, and a second branch extending from the feed 111B includes a conducting strip 114B. The conducting strip 114B extends from the feed 111B to the gap between the branch and the second resonator 115B. The delay line 113B in the first branch is configured to produce a phase shift relative to the conducting strip 114B in the second branch.
As shown in
As shown in
In the example shown in
In the example shown in
In some implementations, a delay line in a branch of a balun can be configured to produce a 180-degree phase shift, relative to another branch in the balun. The example delay lines 113A, 113B shown in
The example resonator device 100 shown in
In some aspects of operation, the sample 110 is positioned on the substrate 160 in the sample region 105 between the resonators 115A, 115B. The sample 110 can be, for example, a magnetic resonance sample that includes an ensemble of electron spins or nuclear spins. The principal magnetic field B0 can polarize the spins in the sample 110. The spins have a resonance frequency (or spin precession frequency) in the principal magnetic field B0. The resonance frequency is typically in the MHz or GHz range (radio or microwave frequencies) in magnetic resonance applications. In operation, the resonators 115A, 115B are fed differentially by the baluns 102A, 102B and generate a microwave field at their resonance frequency. The time-varying field can be tuned to the resonance frequency of the spins in the sample 110, for instance, to manipulate the spins.
In some aspects of operation, the microwave signal is fed into the baluns 102A, 102B at their respective feeds 111A, 111B, and the microwave signal is divided equally into the two transmission lines formed by the branches in each of baluns 102A, 102B. The baluns 102A, 102B are each configured to convert the microwave signal to a pair of balanced microwave signals with 180 degrees phase difference at the ends of the transmission lines. One of the transmission lines in each of the baluns 102A, 102B includes the delay line, and the microwave signal through the delay line traverses a longer electrical path than the microwave signal through the other transmission line (i.e., the transmission line without the delay line). Relative to the transmission line without the delay line, the transmission line with the delay line provides 180 degrees more electrical length for signals at the resonance frequency of the resonators 115A, 115B. The relative difference in electrical length produces a relative phase shift in the signals at the output of the baluns 102A, 102B. The relative phase shift produces the pair of balanced signals that are communicated from the baluns 102A, 102B to the resonators 115A, 115B.
In some aspects of operation, the baluns 102A, 102B drive the two resonators 115A, 115B through the capacitive gap at the ends of the resonators 115A, 115B. The baluns 102A, 102B are symmetrically arranged on opposite sides of the resonators 115A, 115B. In the example shown, the symmetric two-port arrangement satisfies the impedance matching condition over a large range of the gap size which is used for quality factor adjustment. Each of the delay lines 113A, 113B can apply a 180-degree phase shift to the microwave signal that is fed into the first resonator 115A, relative to the phase of the microwave signal that is fed into the second resonator 115B. As such, the phase shift produced by the delay line 113A compensates for the phase shift produced by the other delay line 113B.
In some aspects of operation, the resonators 115A, 115B are simultaneously excited at a single resonance frequency corresponding to the odd mode. The resonators can be excited differentially and carry the same current distributions in opposite directions. In such instances, the magnetic fields generated by the two resonators 115A, 115B constructively add in the sample region 105. When operated as half-wavelength resonators, the current over the length 133 of the resonators 115A, 115B has a cosine distribution. In such instances, the magnetic field generated by the resonators 115A, 115B is at a maximum in the sample region 105 where the sample 110 resides. In the example shown, the direction of the magnetic field generated by the resonators 115A, 115B is oriented in the y-direction (perpendicular to the xz-plane). Thus, the spin ensemble in the sample 110 experiences microwave-frequency magnetic field that is primarily oriented in the y-direction, which is perpendicular to the principal magnetic field B0 (oriented in the z-direction).
In some instances, the example resonator device 100 can be operated to produce a time-varying magnetic field in the sample region 105. For example, the resonator device 100 may produce a microwave frequency field configured to manipulate spins in the sample 110. In some instances, the example resonator device 100 can be operated to produce a detection signal. The detection signal can be produced by a voltage induced across the resonators 115A, 115B by precession of spins in the sample 110. For example, the spins can inductively couple to the resonators 115A, 115B as the spins precess in the principal magnetic field B0. The resonators 115A, 115B can transfer the detection signal to the feeds 111A, 111B. The feeds 111A, 111B can transfer the detection signal to an external system, where it can be detected, recorded, and further processed.
In the example shown in
In the example shown in
The example delay line 113C shown in
In the example resonator device 200 shown in
The example delay lines 113C, 113D shown in
In some systems, the perpendicular component of an RF or microwave magnetic field impinging a perfect conductor is zero. To reduce the mode volume of the resonators 115A, 115B, two conductor strips 116A, 116B may be positioned on the sides of the sample 110. In the example shown in
The source 902 includes a microwave voltage source Vs coupled between ground and a source resistance Rs. The source 902 is shown with a current Iin and impedance Zin. The baluns 904, 910 each include a 180 degree phase shift in one of the lines. Each of the baluns 904, 910 is shown with an impedance Z0, a current I1, and a coupling coefficient γ0. The coupled resonators 908 each include 180 degree phase shift in both of the lines. Each of the coupled resonators 908 is shown with an impedance Z0o, a current I0, and a coupling coefficient γ0o. The coupling capacitors 906, 910 each include capacitances Cs. The load 914 includes a load resistance RL connected to ground.
In a general aspect of what is described, a resonator device includes a delay line.
In a first example, a resonator device includes a dielectric substrate; a ground plane on a first side of the substrate; conductors on a second, opposite side of the substrate; and a sample region configured to support a magnetic resonance sample between the first and second resonators. The conductors include first and second resonators and two baluns. The baluns each include a respective feed, a first branch and a second branch. The feed of each balun is connected to the first and second branches of the balun; and the first and second branches of each balun are capacitively coupled to the respective first and second resonators. The first branch of each balun includes a delay line configured to produce a phase shift relative to the second branch of the balun.
Implementations of the first example may include one or more of the following features. The delay line can extend between first and second ends of the delay line. The first branch can include a first portion connected between the feed and the first end of the delay line, and a second portion connected to the second end of the delay line, extending to a gap between the first branch and the first resonator. The second branch can extend from the feed to a gap between the second branch and the second resonator. The delay line can include a first delay line portion that extends from the first end of the delay line, perpendicular to the first portion of the first branch; a second delay line portion that extends from the second end of the delay line, perpendicular to the second portion of the first branch; and one or more turns between the first and second delay line portions. The delay line can include a third delay line portion that extends from the first delay line portion, perpendicular to the first delay line portion; a fourth delay line portion that extends from the second delay line portion, perpendicular to the second delay line portion; and one or more turns between the third and fourth delay line portions. The first and second resonators can include first and second elongate resonator strips, and the third and fourth delay line portions can extend in a direction parallel to the first and second resonators.
Implementations of the first example may include one or more of the following features. The delay line can be configured to produce a 180-degree phase shift, relative to the third branch, in an electromagnetic signal at a resonance frequency of the first and second resonators. The feed can have a first characteristic impedance, and the first and second branches can have respective characteristic impedances greater than the first characteristic impedance. The first and second branches can have twice the characteristic impedance of the feed. The conductors can be made of superconducting material. The first and second resonators can be half-wavelength resonators. The conductors on the second side of the substrate can include strips about the sample region, between the first and second resonators.
Implementations of the first example may include one or more of the following features. The resonator device can be configured for installation in a magnetic resonance system that generates a principal magnetic field. The first and second resonators can include first and second elongate resonator strips that extend parallel to the principal magnetic field.
In a second example, a resonator device includes a first resonator, a second resonator, a sample region configured to support a magnetic resonance sample between the first and second resonators, and means for delivering microwave signals to the first and second resonators. The microwave signals delivered to the first resonator have a phase that is shifted, relative to the microwave signals delivered to the second resonator, by the means for delivering microwave signals.
Implementations of the second example may include one or more of the following features. The means for delivering microwave signals can include a balun. The balun can include a feed, a first branch and a second branch. The feed can be connected to the first and second branches. The first and second branches can be capacitively coupled to the respective first and second resonators. The first branch can include a delay line configured to produce the phase shift. The means for delivering microwave signals can include a first balun comprising a first pair of branches capacitively coupled to the respective first and second resonators; and a second balun comprising a second pair of branches capacitively coupled to the respective first and second resonators. The first and second resonators and the first and second baluns can include superconducting material on a dielectric substrate. The resonator device can include the dielectric substrate and a ground plane. The dielectric substrate can support the first and second resonators and the means for delivering microwave signals.
While this specification contains many details, these should not be understood as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular examples. Certain features that are described in this specification or shown in the drawings in the context of separate implementations can also be combined. Conversely, various features that are described or shown in the context of a single implementation can also be implemented in multiple embodiments separately or in any suitable subcombination.
Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single product or packaged into multiple products.
A number of embodiments have been described. Nevertheless, it will be understood that various modifications can be made. Accordingly, other embodiments are within the scope of the following claims.
Cory, David, Teklemariam, Grum, Mohebbi, Hamidreza
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